* This document contains certain information on a new product.

Specifications and information herein are subject to change without notice.

Document Number: MC34845

Rev. 2.0, 9/2009

Freescale Semiconductor

Advance Information

© Freescale Semiconductor, Inc., 2009. All rights reserved.

Low Cost 6 Channel LED

Backlight Driver with Integrated

Power Supply

The 34845 series represents high efficiency LED drivers for use in

backlighting LCD displays from 10” to 17”+. Operating from supplies of

5.0 V to 21 V, the 34845 series is capable of driving up to 16 LEDs in

series in 6 separate strings. The LED current tolerance in the 6 strings

is within ±2% maximum and is set using a resistor to GND.

PWM dimming is performed by applying a PWM input signal to the

PWM pin which modulates the LED channels directly. An Enable Pin

(EN) provides for low power standby. Alternatively, a single wire

scheme selects power down when PWM is connected to the Wake Pin

and held low.

The integrated boost converter uses dynamic headroom control to

automatically set the output voltage. There are three device versions for

boost frequency; 34845 is 600 kHz, 34845A is 1.2 MHz and the 34845B

is 300 kHz. External compensation allows the use of different inductor/

capacitor combinations.

The 34845 includes fault protection modes for LED short and open,

over temperature, over current and over voltage errors. It features an

internally fixed OVP value of 60 V (typical) which protects the device in

the event of a failure in the externally programmed OVP. The OVP level

can be set by using an external resistor divider.

Features

• Input voltage of 5.0 to 21 V

• Boost output voltage up to 60 V

•2.0 A integrated boost FET

• Fixed boost frequency - 300 kHz, 600 kHz or 1.2 MHz

• OTP, OCP, UVLO fault detection

• LED short/open protection

• Programmable LED current between 3.0 mA and 30 mA

• 24-Ld 4x4x0.65 mm

μQFN Package

Figure 1. 34845 Simplified Application Diagram

34845

34845A/B

LED DRIVER

98ASA00087D

24-PIN QFN-EP

ORDERING INFORMATION

Device

Temperature

Package

MC34845EP/R2

-40° to 85°C

24 QFN-EP

MC34845AEP/R2

MC34845BEP/R2

Tape and Reel depicted with “R2”

12V

FAIL

PGNDB

34845

SWA

SWB

VOUT

PGNDA

CH1

CH2

CH3

CH4

CH5

CH6

EP

EN

PWM

ISET

VIN

VDC1

VDC2

COMP

WAKE

~

~ ~

~

~

~ ~

~ ~

~ ~

~

OVP

GND

GND

CONTROL

UNIT

5V

Typical Applications

• PC Notebooks

• Netbooks

• Picture Frames

• Portable DVD Players

• Small Screen Televisions

• Industrial Displays

• Medical Displays